Tapered plastic containers with snap on or screw on closures have become increasingly popular for packaging food products, particularly fresh fruit, salad and dairy products. Such containers provide economies in packaging and convenience to the consumer in use, reclosure and storage. Containers of this type which are often provided with decorative designs have typically been offered to the consumer in open ended enclosing sleeves which facilitate display and stacking of product in supermarkets. Sleeve packages also provide space for brand names and product information.
Sleeves presently finding wide application have a generally rectangular or trapezoidal configuration and are dimensioned to frictionally receive housed containers. In order to prevent dislodgement of the containers slots or notches are typically provided in opposing side walls of the sleeve to engage the container closure lid which includes a peripheral edge or flange projecting outward from the container body. Engagement of the closure within such retention slots secures the container in the sleeve.
It has been recognized in the art, however, that frictional retention sleeve arrangements are not entirely satisfactory in guarding against tampering of food products. Difficulty has been presented by the relative ease with which the consumer may remove and replace containers with more expensive products without damage to the sleeve or evidence of tampering. It will be appreciated that a tamper-proof feature is also important for assuring product integrity and safety.
The packaging industry has proposed various sleeve retention structures which have not proved to be commercially satisfactory. An early approach is exemplified by U.S. Pat. No. 2,274,253 to Howell which is directed to an open ended sleeve which slidably receives a container. The sleeve includes a front wall having hingedly attached opposing wings which pivot about crease lines and are received within the open ends of the sleeve. Each wing has a curved edge which respectively engage an annular indentation in opposing sides of the cover to secure the container within the sleeve. This structure is not effective in that the retention wings may be readily disengaged by the consumer and again fastened in place without revealing evidence of tampering.
Another approach of the prior art is disclosed in U.S. Pat. No. 3,604,560 to Farquhar which shows an open ended sleeve which includes extension flaps extending from end edges of a bottom wall. Each extension flap includes a plurality of fold lines which define an end stop for the enclosed container, and a locking tab arrangement to secure the stop and evidence tampering. Fundamentally, difficulty is presented by the complex pattern of score lines and folding operations required to construct the sleeve with associated machining and packaging costs. Specifically, each extension flap includes a score pattern which requires bifolding of panel sections to define the stop which includes a locking tab, and arcuate legs for conforming engagement with a container. Following this folding operation the container is placed within the sleeve and the bifolded extension flap is pivoted into vertical orientation with respect to the open end of sleeve to engage the locking tab with a corresponding tongue to define a closure. Machining accuracy and costs are associated with the performance of required folding and locking operations in proper sequence.
Other approaches of the prior art are similarly characterized by complex folding structures which have not proved to be entirely satisfactory. Such further approaches of the art are represented by the following U.S. Pat. Nos. 2,738,055 to Shanahan; 3,618,848 to Pawlowski; 3,765,529 to Mueller; and 4,416,411 to Desmond.
The present invention is directed to a sleeve construction having a retention structure of uncomplex design which is compatible with conventional packaging machinery and provides enhanced effectiveness over prior art arrangements. It will be appreciated that an effective retention structure which does not require extensive retooling of conventional sleeve machinery will effect cost savings and a meet a need of the packaging art.
Accordingly, it is a broad object of the present invention to provide an improved sleeve of uncomplex design which incorporates a tamper-proof retention feature.
A more specific object of the invention is provide a sleeve construction including a retention and tamper-proof structure which is cost effective in material and compatible with conventional sleeve forming machinery.